JOURNAL OF THE BRAZILIAN CHEMICAL SOCIETY
·
2018
·Vol. 29
·期 2
·404-411
·
IF 1.444
Song Jia-Xing,Fang Xiang,Guo Tao,Bei Feng-Li,Ding Wen,Zhang Xiao-Nan,Yao Miao,Yu Hong-Jun
In this work, thermal properties and kinetics of Al-nanoparticles/α-MnO2 nanorods thermite were reported. The α-MnO2 nanorods were synthesized using a hydrothermal method and were characterized by X-ray powder diffraction (XRD) and X-ray photoelectron spectra (XPS), then combined with Al nanoparticles based on the ultrasonic mixing method to prepare the nanostructure thermite. Besides, both pure components and mixture were characterized by field emission scanning electron microscopy (FE-SEM) to observe their morphologies and structures. Subsequently, the thermal properties of Al/α-MnO2 nanostructure thermite were studied on the basis of thermogravimetric-differential scanning calorimetry (TG-DSC). According to the TG-DSC tests, the calculation results of activation energy for kinetics of Al/α-MnO2 thermite were obtained using different isoconversional methods. It was found that Al/α-MnO2 nanostructure thermite has high heat release and low onset temperature, and the heat release of the nanostructure thermite was approximately 1146.6 J g -1.
研究领域:
材料科学
·
热化学
✓ 已验证
DOI
高影响因子
JOURNAL OF ELECTRONIC MATERIALS
·
2019
·Vol. 48
·期 7
·4653-4659
·
IF 1.676
Lei Dongling,Ma Shiyu,Lu Youcai,Liu Qingchao,Li Zhongjun
A rechargeable Li-CO 2 battery has been considered to be a promising battery system due to its high-energy density and the utilization of carbon dioxide (CO 2 ). However, the high overvoltage caused by the discharge product Li 2 CO 3 hinders the development of Li-CO 2 batteries. In this work, α-MnO 2 nanowires obtained via a redox reaction have been employed as the cathode catalyst in the Li-CO 2 battery, which can provide sufficient catalytic sites for CO 2 evolution and tune the cathode structure for the uniform distribution of Li 2 CO 3 and C on the cathode. The Li-CO 2 battery with an MnO 2 /carbon nanotube (CNT) cathode exhibits significantly reduced overpotential, and could be operated for 50 cycles with a fixed capacity of 1000 mAh g −1 and 6 cycles of full discharge–charge tests at a current density of 100 mA g −1 .
研究领域:
材料科学
·
电化学
✓ 已验证
产品关联
DOI
高影响因子
RSC Advances
·
2017
·Vol. 7
·期 74
·46529-46535
·
IF 3.108
Hengfa Liu,Bentian Zhang,Wanping Li,Gao Cheng,Jiaxi Han,Bang Lan,Ming Sun,Lin Yu
Hierarchical pine tree-like α-MnO2 architectures are prepared by a facile one-step method without any template. The hierarchical α-MnO2 is composed of branched α-MnO2 short nanorods assembled onto the backbone of an α-MnO2 long nanowire. Time-dependent experiment shows that the growth process of the branched α-MnO2 nanostructures is the formation of β-MnOOH and then the transformation to a α-MnO2 branched structure in a step by step manner. Owing to its specific structure features, the hierarchical pine tree-like α-MnO2 exhibits superior catalytic performance in the catalytic combustion of dimethyl ether with a light-off temperature (T10) at 169 °C and a complete conversion temperature (T90) of 235 °C, which is far better than commercial MnO2.
研究领域:
材料科学
·
催化化学
✓ 已验证
DOI
高影响因子
International Journal of Electrochemical Science
·
2023
·
IF 1.5
Hongdong Liu,Zhongli Hu,Yongyao Su,Rong Hu,Liangliang Tian,Lei Zhang,Haibo Ruan
Manganese dioxide (MnO 2 ) has been studied as an anode material for Li-ion batteries beyond its high theoretical specific capacity and low-cost. In this work, the 1D α-MnO 2 nanomaterials with different morphology were synthesized via a facile and green hydrothermal method. These materials are carefully investigated by XRD, Raman, SEM and BET techniques. The results show that the solution acidity strongly influenced the morphology and the specific surface area of the sample. The electrochemical behaviors of MnO 2 sample were systematically investigated by cyclic voltammetry and galvanostatic charge-discharge. As anode materials for Li-ion batteries, both of 1.2-MnO 2 and 3.6-MnO 2 deliver high initial discharge capacity and relatively excellent cycle performance, indicating that 1D α-MnO 2 is a promising anode material for high-performance lithium ion batteries.
研究领域:
材料科学
·
能源存储
✓ 已验证
DOI
高影响因子
CRYSTENGCOMM
·
2021
·Vol. 23
·期 43
·7602-7614
·
IF 3.545
Chao Feng,Gaoyan Xiong,Yaping Li,Qianqian Gao,Yuan Pan,Zhaoyang Fei,Yanpeng Li,Yukun Lu,Chenguang Liu,Yunqi Liu
Determining the effect of crystal facets on reaction performance is essential for designing an efficient propane oxidation catalyst. Herein, α-MnO2 nanowires with exposed (110), (211), (310) and (200) facets were proposed, and their crystal facet-dependent reactivity to propane oxidation was investigated. The resultant α-MnO2 nanowires with predominantly exposed (110) facets showed the maximum propane oxidation activity (T90 = 262.1 °C), oxidation rate, and turnover frequency (at 230 °C), and high stability during the oxidation of propane. In situ diffuse reflectance infrared Fourier transform spectroscopy revealed that the oxidation to form carboxylates is the decisive step; therefore, the production of reactive oxygen species is very important. The results from density of states computations revealed that the lowest electron energy was present in the (110) facet, which helps in the generation of reactive oxygen species and the regulation of the surface valence of Mn. The characterization and calculation results indicated that the (110) facets are conducive to forming oxygen vacancies, which allowed the activation and adsorption of O2 and propane, resulting in significantly enhanced propane oxidation activity. Apart from offering new insights about the structure–activity relationship of α-MnO2 with different facets exposed for short-chain volatile oxidation reactions, this study proposes a technique that can be used for improving other manganese-based catalyst oxidation systems.
研究领域:
材料科学
·
催化化学
✓ 已验证
DOI
高影响因子
CHEMICAL ENGINEERING JOURNAL
·
2018
·
IF 6.735
Zhengyu Dong,Qian Zhang,Bor-Yann Chen,Junming Hong
A novel and high-efficiency Fe 3 O 4 -α-MnO 2 nanoflower-like catalyst was synthesized using a two-step hydrothermal method. The catalyst was used to activate persulfate (PS) to degrade bisphenol A (BPA) in aqueous phase. The mechanism of the Fe 3 O 4 -α-MnO 2 /PS system was investigated. X-ray photoelectron spectra and cyclic voltammograms showed that the mixed valence of Fe 3 O 4 -α-MnO 2 was favorable to electron transfer between Fe and Mn elements. Apparently, this process promoted the circulation of Fe 2+ /Fe 3+ and Mn 3+ /Mn 4+ , increasing the effectiveness of the catalyst to activate the PS. In addition, with ATR-FTIR analysis, the influence of phosphate confirmed the presence of OH groups on the Fe 3 O 4 -α-MnO 2 surface. Thus, these groups played crucial roles in the PS activation . Sulfate radicals were reacting species of great importance in BPA degradation. The degradation intermediates were also detected via GC–MS analysis, and the possible BPA degradation pathway was proposed.
研究领域:
环境科学
·
催化化学
✓ 已验证
DOI
高影响因子
JOURNAL OF ALLOYS AND COMPOUNDS
·
2019
·
IF 4.175
Lidong Sun,Nian Li,Shudong Zhang,Xinling Yu,Cui Liu,Yongqiang Zhou,Shuai Han,Wenbo Wang,Zhenyang Wang
Porous carbon composite electrodes have attracted extensive attention due to their excellent electrochemical performance toward energy storage applications. In this work, hierarchical nitrogen-containing porous carbon (HNPC) and α-MnO 2 nanowires composite electrode is prepared through a template method. The as-prepared composite electrode, characterized as one-dimensional nanowires inserted into three-dimensional interconnected porous structures, exhibits high specific capacitance of 204.6 F g −1 at 1 A g −1 and excellent cycling stability (97.2% remains after 5000 cycles). Moreover, the fabricated asymmetric supercapacitor based on HNPC//HNPC/MnO 2 achieves a wide working voltage window of 1.8 V and a high energy density up to 30.1 Wh kg −1 at a power density of 900.0 W kg −1 . The results indicate that the HNPC/MnO 2 composite electrodes with excellent electrochemical performance have promising perspective in supercapacitor applications.
研究领域:
材料科学
·
能源存储与转换
✓ 已验证
产品关联
DOI
高影响因子
APPLIED SURFACE SCIENCE
·
2023
·
IF 6.7
Hongzhi Chen,Ke Tian,Taiping Qing,Xiaoqing Liu,Jiangling Mao,Jingxi Qin,Shunfeng Jiang
The development of efficient and environmentally friendly catalysts for activating persulfate is the focus of advanced oxidation treatment of organic contaminants. Manganese dioxide (MnO 2 ), which has a multivalent nature and is a low-toxic natural stock, has the ability to immediately oxidize pollutants. In order to further improve its catalytic performance, the α-MnO 2 nanofiber coated with graphene oxide (α-MnO 2 @GO) was prepared by one-step hydrothermal method, and worked as a peroxmonsulfate (PMS) activator for efficient degradation of tetrabromobisphenol A (TBBPA). The structure characterization results indicate that α-MnO 2 nanofibers are successfully encapsulated by graphene and assembled into a three-dimensional layered structure. The factors affecting the catalytic degradation of TBBPA by this catalyst are investigated in detail. Under optimal conditions, the highest removal ratio of TBBPA could reach 100% after treatment of 20 min by α-MnO 2 @GO/PMS system, and a good mineralization efficiency of up to 79.50% is obtained. Electron paramagnetic resonance detection combined with quenching experiments showed that sulfate radical and hydroxyl radical played a role in the degradation of TBBPA. Based on X-ray photoelectron spectroscopy and free radical scavenging experiments, the peroxmonsulfate activation mechanism by α-MnO 2 @GO was proposed. Finally, based on the discovered intermediates, two potential TBBPA degradation routes using this catalyst were suggested. This study not only provides a new strategy for improving the catalytic activity of MnO 2 but also sheds new insight into the application of eco-friendly natural stock for environmental remediation.
研究领域:
环境科学
·
催化化学
✓ 已验证
产品关联
DOI
高影响因子
CATALYSIS TODAY
·
2015
·
IF 3.893
Faheem Nawaz,Yongbing Xie,Hongbin Cao,Jiadong Xiao,YueqiuWang,Xihua Zhang,Mingjie Li,Feng Duan
Two series of α-MnO 2 materials were prepared via a similar method with surfactant cetyltrimethylammonium bromide (CTAB) and sodium dodecyl benzene sulfate (SDBS). The surfactants work both as shape directing agent and reduction initiator. The α-MnO 2 synthesized with 0.2 M of CTAB showed a mesoporous structure with high surface area of 387.7 m 2 /g. It is very active in catalytic ozonation of 4-nitrophenol (4-NP) and total organic carbon removal, with higher catalytic stability than commercial MnO 2 . Using tert -butanol and p -benzoquinone as scavengers of different oxidative species, we found that superoxide radicals, rather than hydroxyl radicals, were mainly responsible for the degradation of 4-NP.
研究领域:
环境科学
·
材料科学
✓ 已验证
DOI
高影响因子
ACS Applied Materials & Interfaces
·
2016
·
IF 7.145
Wen She,Han Bi,Zhiwei Wen,Qinghe Liu,Xuebing Zhao,Jie Zhang,Renchao Che
A tunable response frequency is highly desirable for practical applications of microwave absorption materials but remains a great challenge. Here, hollow lightweight polydopamine@α-MnO2 microspindles were facilely synthesized with the tunable absorption frequency governed by the aspect ratio. The size of the hard template is a key factor to achieve the unique shape; the polymer layer with uniform thickness plays an important role in obtaining spindles with homogeneous size. With the aspect ratio increasing, the maximum reflection loss, as well as the absorption bandwidth (<−10 dB), increases and then decreases; meanwhile, the microwave absorption band shifts to the low frequency. The optimized aspect ratio of the cavity about the hollow polydopamine@α-MnO2 microspindles is ∼2.8. With 3 mm thickness at 9.7 GHz, the strongest reflection reaches −21.8 dB, and the width of the absorbing band (<−10 dB) is as wide as 3.3 GHz. Via electron holography, it is confirmed that strong charge accumulates around the interface between the polydopamine and α-MnO2 layers, which mainly contributes to the dielectric polarization absorption. This study proposes a reliable strategy to tune the absorption frequency via different aspect ratio polymer@α-MnO2 microspindles.
研究领域:
材料科学
·
电磁学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
Catalysis Science & Technology
·
2016
·Vol. 6
·期 20
·7429-7436
·
IF 5.287
Xiuquan Jia,Jiping Ma,Min Wang,Xiaofang Li,Jin Gao,Jie Xu
The tandem reaction is a growing field to yield important advances toward green and sustainable chemistry. Herein, we report a bifunctional manganese oxide catalyst with an interface binding redox phase (α-MnO2) and a basic phase (NaxMnO2). The molar ratio of NaOH/Mn plays a great role in the formation of α-MnO2/NaxMnO2. The sodium cation is essential for the formation of a basic NaxMnO2 phase while the potassium cation promotes the formation of a redox-active α-MnO2 phase. The interface structure of α-MnO2/NaxMnO2 geometrically favors the ammoxidation–Pinner tandem reaction to synthesize imidates in a 58–96% yield from aldehydes. Thus a phase collaborative effect is observed. In the ammoxidation process, the redox cycle of MnIV/MnIII is involved and the lattice oxygen in the α-MnO2 phase acts as an active oxygen species. The O–H in methanol is activated and dissociated on the basic sites of NaxMnO2 to the adsorbed methoxyl species to facilitate the Pinner synthesis. This approach bypasses the conventional synthesis of imidates, which suffer from harsh reaction conditions and the requirement for multiple steps.
研究领域:
催化化学
·
材料科学
·
有机合成
✓ 已验证
产品关联
DOI
高影响因子
MATERIALS CHEMISTRY AND PHYSICS
·
2013
·
IF 2.072
Hongtao Guan,Jianbin Xie,Gang Chen,Yude Wang
One-dimensional α-MnO 2 nanorods were fabricated by using low-temperature water-bathing chemical precipitation method at 80 °C. The crystalline structures, morphological evolution process and microwave absorption properties were systematically investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and measurement of electromagnetic parameters. The results show that the morphological structures and electromagnetic properties have close relationship with the reaction time. With the prolonging of the treatment time, the as-synthesized products turn from microspheres constituted of tiny dendrites to nanorods with diameters of 20–30 nm and lengths up to 1–2 μm. The electromagnetic characterization shows that the dielectric constants and magnetic permeability values show decreasing trends with the increasing frequency, however, the dielectric and magnetic loss tangents all increase with frequency. The electromagnetic absorption properties of the products have close relationship with the morphologies and thicknesses of the samples. With a thickness of 3 mm, an absorbing peak value of −25 dB was achieved for the sample treated for 24 h. The microwave absorption properties of MnO 2 can be attributed mainly to interfacial polarization, space charge polarization and relaxation phenomena.
研究领域:
材料科学
·
化学工程
✓ 已验证
DOI
高影响因子
危险品化学品经营许可证（带存储）